Switching arrangement for automatic telephone systems



Sept. 13, 1960 E. EHRICKE ETAL SWITCHING ARRANGEMENT FOR UTOMATIC TELEPHONE SYSTEMS Filed lay 19, 1955 4 Sheets-Sheet 1 Sept. 13, 1960 E. EHRlcKE ETAL 2,952,741

SWITCH-[NG ARRANGEMENT FOR AUTOMATIC TELEPHONE SYSTEMS Filed may 19, 195s 4 sheets-sheet 2 lllL Sept. 13, 1960 E.EHR1CKE ErAL- 2,952,741

SWITCHING ARRANGEMENT FOR AUTOMATIC TELEPHONE SYSTEMS 4 Sheets-Sheet 3 Filed May 19, 1955 Sept. 13, v196() Filed May 19.l 1955 EGW E. EHRICKE lET AL SWITCHING ARRANGEMENT FOR AUTOMATIC TELEPHONE SYSTEMS 4 sheets-sheet 4 0 x I @H55 United States Patent() lSWITCI-IING ARRANGEMENT FOR AUTOMATIC TELEPHONE SYSTEMS .Erich Ehricke, Munich, and Ferdinand 'Johannes Dreyer, also known as Hans Dreyer, deceased, late of Munich, Germany, by Elisabeth Dreyer, geb. Hemming, administratrix, Munich, Germany, assignors to Siemens Y8a Halske Aktiengesellschaft Berlin and Munich,

Munich, Germany, a `corporation of Germany Filed May 19, 1955, Ser. No. 509,494 In Germany Feb. 1, 1950 Public Law 619, Aug. 23, 1954 Patent expires Feb. 1, 1970 `8 Claims. (Cl. 179-18) This invention is concerned with a switching arrangement for automatic telephone systems.

In telecommunication and particularly in automatic telephone systems, it is frequently necessary to transmit, from the connector back over the communication path which has been established, a signal yindicating the conclusion of dialing. The dialing-conclusion signalmay be differently utilized in the switching devices'preceding the connector depending on the system.

Thus, for instance, in systems employing registers and translators, the register which operates on the subscribers numbers is given a dialing-conclusion signal so as to cause disconnection thereof from the established connection. In other telephone systems, the .dialing-conclusion .signal may be transmitted to prevent further dialing by a calling subscriber in a telephone network connection to elect special switching operations over the same line in toll calls. This should be possible only for the .toll operator. The toll operator, furthermore, after the setting of the connector to the desired line, has the possibility of dialing in order to connect with a busy line or to call back upon conclusion of a call. In such systems, the dialing-conclusion signal eliminates the neces- .sity for a special toll signal in order to distinguishlocal calls from toll calls. A further possibility of the use of the dialing-conclusion signal resides in switching through a channel opened during the extension of a call. The dialing-conclusion `signal may also be used to eiect a switching operation only in the last incoming repeater, thus permitting transmission of other signals, for instance, check back or verification signals in long distance calls. Atoll callwill, in such cases, diler from an automatically .dialed call by a special long distance signal, which eiects switching in the incoming repeater bythe dialing-conclusion signal only inthe case of toll calls.

It has already 'been proposed to transmita dialing- `conclusion signal back from the connector inthe form Aof pulses. This must take place'upontermination of the setting of the connector because, during the dialing, Yat

leastone of the lineeonductors of the connecting pathfor `the pulse transmission, and in most cases also the other 'line conductor for switching'operations'connected with the Vtdialing, is occupied, for instance ffor the 'controlling of `the selectors. Such an arrangementaiordsdi'ieulties Iwithregard to theproper moment-ofoccurrence and the ,correct lengthroftthe dialing-conclusion pulses. These diiculties may be overcome only by increased expendi- .tureand `correspondingly high costs.

In order to avoid vthese difficulties, the .presentinvention utilizes the fact that in existing telephone systems, in

-allstages provided forthe building up of avconnection (group selectors, repeaters, connectors, I etc.) -a given rpo .tentiaL for instance ground, or else no potential, is ap- .plied toone of the line conductors, makingpossible, Yfor finstance, Athetestingof the -lues'and-connecting devicesas etoitheiroperability.

ice

In accordance with the present'invention, the dialingconclusion signal is produced temporarily or lastiugly by changing and preferably disconnecting at the end of the selection operation the potential applied inall connecting devices of a connection for given switching operations'to a line conductor, for instance, ground potential applied in the connector, such change being effected by switching means responsive to receipt of the receiving of ldial pulses; switching means being provided in apreceding connecting device for testing, step by step, the connecting devices lying in the connecting paths with respect to this potential, and utilizing solely the change of potentialin the connector. The disconnecting of the ground po- 'tential in the connector takes place suitably before'the last series of dial pulses is received.

This solution has the particular advantage that therequired switching means can be more easily installed -in by the connector at a very early stage, namely, even be- Vfore the completion of ithe dialing, mutilations of the signal by further dialing on the part of the calling subscriber cannot take place. Finally, the arrangement in accordance with the invention is considerably less expensive because the switching operations for the required signal criterion must betaken care of not in a large number of connectors present, but rather in the line -repeaters which are present only in considerably smaller number.

An embodiment of the invention will now be described with reference to the accompanying drawings in which Pig. l shows an overall circuit diagram to aid -in describing respectively a directly dialed call and a toll call; and

Figs. 2 to 4 show details of vconnecting devices necessary for an understanding of the invention.

In the main exchange HA, a local call may be established Vfor instance between subscribers T111 and Tn?2 `over a first preselector lVW, a lirst group selector suchas IGW and a connector such as LW1. The subexchange UA may be reached, in the case of directly dialed calls,

by the subscriber of the main exchange HA over the `trunk lines VL only one of which is shown in order to -keep the drawing simple.

Trunk line VL, which may be radapted for .alternating current operation, is reached lby dialing a code number over a iirst groupselector such f-as IGW of the main exchange HA. Associated with each trunk line is an outgoing A.C. repeater Uel anda so-called time-zone unit ZZ which is set by the code signal transmitted Vby the calling subscribers. At the other .end

of the trunk line in the subexchange UA, there is disposed an"incoming.A.C. repeater Ue2, which is connected to ia second group selector IIGW. Over this group selector Ais .reached the connector LWZ which has access to the subscriber Tn3.

.To the iirst group selector IGW ofthe main exchange HA, there is multiply connected a toll group selector ZFGW which is accessible to the toll operator position FPL. The toll operator position FPL has access over this `toll1 group selector F GW both to connectors such as LWl of themain exchange HA and to trunk lines such as VL.

For making toll calls, the toll operator must have the possibility to transmit in customary manner special switching signals, for instance, signals for establishing connection 'to a busy subscribers line or for recalling a desired line.

This problem is solved by the dialing-conclusion signal.

on the pulse transmission proceeding from the toll operator position FPL, the toll operator can transmit current pulses after the setting of the connector LW2 so as to -build up the connecting or ringing current circuits in the connector. y t

Figs. 2, 3 and 4 show switching details of the successive .connecting devices which are occupied during a directly A dialed connection call on the part of a subscriber of the :main exchange, namely, the time-zone unit ZZ, outgoing A.C. repeaterfUel, incoming A.C. repeater Ue2, second -group selector IIGW and connector LW2.

vIn the following description, the plus symbol indicates the positive pole, ywhich as a rule is grounded, while the Vminus symbol indicates the negative pole of the exchange battery. In order to make a directly dialed call, a calling subscriber of the main exchange HA (-Fig. l) has, let us Aassume, seized the time-zone unit ZZ ('Fig. 2) over a preselector lVW and thefirst group selector =1GW. Over VVthe private or c-conductor of the irst group selector, the seizure relay CZ energizes which closes its contact CZ2 to the private or c-conductor of the outgoing repeater Uel to eiect seizure thereof. 1n the repeater Ue.1 (-Fig. 2), l relay A1, winding I, energizes over the c-conductor. Re- Ylay A1 connects seizure relay `C1 in series with the Winding IIII of relay A1 in the following circuit: '3v1, 5111, v2g1, 2m1, 3k1, C11, A1111 to. When relay A1 energizes, an A.C. pulse is transmitted to the trunk line VL from a .source WQ1 over contacts 5111, `6111 of relay A1. The vA.C. pulse is terminated by relay A1 connecting relay M=1: -l-, 3v1,'5a1, 2g1, M1, Relay M11 interrupts the circuit for winding 111 of relay A1 and for the winding .1 of the Yholding relay C1 at the contact 2in1. Relay C1 is however held over its winding kI1, contact 2c1 and the incoming c-conductor. Relay A1 releases and, as already mentioned, terminates transmission of the A.C. seizure pulse. After relay A1 releases, relay M1 being energized, relay K1 is energized: 3v1, 311-1, 6m1, 3h1, K1,

""'\ Relay K1 establishes a holding circuit for itself over con- Vtacts 2k1,'4m1 and prepares an energizing circuit for relay G1 at contact 4k1. Relay M1 is held over contact 5ml.

In the incoming repeater Ue2 (Fig. 3) relay E2, winding I, is energized over the c-conductor leading to the second group selector `IIGW and contacts 11e2 and 12e2 vare accordingly closed. The winding I of relay E2 has a high resistance so that the seizure relay of the second group selector cannot energize in this circuit. The current pulse receiving relay J2 is briey energized by the incoming seizure pulse. Relay I2 connects the seizure relay O2: C2, E211, 2c2, 3112, 711:2, 8]'2, 1n this circuit, winding I1 of relay E2 is traversed by current so as to keep it energized even after the direct grounding of the outgoing c-conductor by contact 9c2 and consequent short-circuiting of its winding I. Relay C2 is after the release of relay 12 held energized over contact 1c2. Relay C2 connects relay A2 over contacts SC2. Relay A2 short circuits relay C2 at contact 34112. However, it is only briey energized by the seizure pulse so that relay C2 does not release. After the release of relay A2, relay U2, winding I is connected over contacts 2302 and 25112. Relay U2 is thereupon held energized, over'its contact 27112, independently of contact 25112 of relay A2.

'In the'second `group selector IIGW (Fig. 4) seizure relay Cg is energized from direct ground on the c-conductor incoming from the repeater Ue2 (Fig. 3). Relay Cg prepares a setting and test circuit for the second group selector. It may be mentioned at'this point that in the normal position of the second group selector, ground is applied to its b-conductor from 111g, lpg, olf-normal contact 2kg, resistor W13. The same is true in a third group selector stageV (not shown), the circuit of which corresponds to that ofthe second grou-p selector. Upon `dialing by the calling subscriber, relay` Az in the time-zone unit ZZ ('Fig. 2) is energized intermittently in known manner. Relay 'Az 'applies -ground intermittently over contact lrzzl toY thea-conductor (line lcontactSk, C11, 7g, 4the'groupselector by opening contact lpg, busies the conductor); at the same time, the slow-to-release relay Vz, energized over contact az2, applies control voltage to the b-cond-uctor (line conductor) at its contact vzl. The ground pulses energize relay A1 in repeater Uel from -l, tz3, czZ, azl, a-conductor, A111, A111, 1h1, The control voltage on the b-conductor does not have any elfect beca-use only a second winding (not shown) of the choke coil Dr is connected with the b-conductor in the repeater Ue1. Relay Al'transmits the received current pulses as A.C. pulses to the trunk line VL by closing the contacts Sal, 6111. Relay V1 is connected by relay A1 in a circuit extending from -l, 2k1, 4111, V11, V111, Relay V1 is held energized during the train of pulses due to the short circuiting of Winding 11 over contact 2v1.

In the incoming'repeater Ue2, the incoming A.C. current pulses are received :by relayV J2. Relay I2 connects relay A2 in a circuit extending from SC2, A2, 8j2, Relay A2 now transmits the current pulses as ground pulses to the aconductor for the second group selector lIIGW (lFig. 4) from 20112, 21112, a-conductor, off-normalcontact'Zwg, Ag, After energiza-tion of relay A2, the slow-to-release relay V2 ('Fig. 3) is energized'in a circuit extending from 23c2, 27112, 24112, V2, 4. Relay V2 is Vmaintained energized during the series of currentpulses. Relay V2, over its contact -16v2 applies control voltage to the b-conductor in a circuit including relay X2. Relay V2 further-more connects 'the slow-to-release relay Y2 over'contact 29v2; relay Y2 Vtor W1'3', 2kg, lpg, 111g, it is maintained energized over the winding during the series of current pulses in a circuit from 2-8x2, 63312, 32x2, X211, The energizing of relay H2 is prevented by the opening of contact 31x2. After the completion of the train or series 'of pulses, relays V2, Y2, X2 deenergize, one after the other.

iIn the second group selector (Fig. 4) the current pulsescoming from repeater Ue2 over Vthe a-conductor 'are received bythe relay Ag in a circuit from 20112, V21112, zz-conductor, olf-normal contact Zwg, AgI, AgII, 45

.vertical magnet Hg and, parallel to it, the winding III 'of the test relayY Pg, which acts as a switch-overrelay RelayAg by means of contact V212g Vconnects the dueto short circuit of its winding Il over contact 4pg. The selector Ylifts its wipersV in known manner responsive to the train of current pulses. Thereupon it rotates the 'wipers Iunder control of the relay Ag, in hunting motion, "to -indhan idle trunk line to a connector LW2. During Ythe setting of the second group selector, ground is applied intermittently for reasons of symmetry to the bconductor (by contact 311g) but this is without effect on therelay. X2 connected to the b-conductor in the repeater Ue2, )since relay X2, as already described, is held locally. Afterthe second lgroup selector has found an idle Vtrunk line, the test relay Pg is energized over the c-con- Vductor (private conductor) to the, connector LW2 in a circuit from Scg, PgI, PgII, c-wiper, 4c, oli-normal Relay Pg stops the hunting of seized trunk by shunting its winding II andr connects the two line conductors a and b through at contacts 3pg, 412g. .Y t

Inthe connector LW2 (Fig. 4), the seizure relay C is 'energized over the c-conductor coming from the second group selector IIGW. 1

The last'two trains of current pulses are transmitted same time, relay X2 is again connected byrelay V2 to the b-conductor; it again tests whether there 'is ground potentialV or not. Since in the connectoras in the group selector stages preceding it-ground potential is on the b-conductor in the normal condition, relay X2r in the repeater Ue2V is again energized in a circuit from 17W2, X21, 116v2, b-conductor, 417gI wiper b, 131111, 2u, olf-normal contact 1w, Relay X2 remains energized until the termination ofthe next to the last train of dial pulses in `a circuit from 28x2, 3'3y2, 32x2, X211,

The ground pulses on the a-conductor coming from the repeater Ue2 energize in the connector relay AY in a circuit from 20a2, 211:2, a-conductor, 3pg, a-wiper, 9g, A, Relay A transmits the pulses over contact 8a to the vertical magnet Ho'f the connector in a circuit including slow-to-release relay V. When the train of pulses terminates and the Wipers of the connector have been raised to the corresponding decade, the slow-to-release relay V deenergizes. The slow-to-release relay U now energizes in series with the vertical magnet H from olf-normal contact 18k, 22V, 17e, U, oinormal co'ntact W, H, The vertical magnet does not operate in this circuit. Relay U, by means of contact 13u shifts the pulse circuit to the rotary magnet D so that upon receipt of the last series of pulses, these pulses are transmitted to the rotary magnet D. Relay U opens contact 2u and thus removes ground from the b-conductor leading to the repeater Ue2.

Upon receipt of the last series of pulses at the incoming repeater Ue2, the relay A2 again intermittently applies ground to the a-conductor. The slow-to-release relays V2 and Y2 are again connected, and relay X2 is connested to the b-conductor. Relay X2 can however no longer beenergized since it doesrnot find ground in the connector. This is the dialing conclusion which is prepared in the connector LW2 after the reception of the next to the last series of pulses (lifting) of connector wipers by disconnecting ground potential from the b-co'n- Vductor at contact 2u and such signal is received in the preceding connecting device upon the beginning of the last series of pulses.

In the connector LW2, the pulse receiving relay A is again energized by the last series of pulses, such relay now actuating the rotary magnet D in a circuit from VI, 8a, 13u, 20p, D, Upon the rst rotary step, the oit-normal co'ntact 1w is opened, which nally removes ground from the b-conductor. I n series with the rotary magnet D, the sloW-to-release relay V is energized. Relay U, after energization ofV relay V, is held energized over a-second-winding (notshown). Whenthe pulses-terminates, the relay G, after the release of relay V, energizes in series with relay U over the slow-speed interrupter LU from -l-, 18k, 22V, 17C, U, 11W, 16g, GI, LU, Relay G opens its energizing circuit at co'ntact 16g, but is held energized over its winding 11 in series with the seizure relay C. Relay U restores with a certain delay. Relays G and U then prepare the test circuit for relay P.

The nal disconnecting of the ground potential from th: b-conductor in the connector could, instead of -being elected by the off-normal contact 1w, also take place as a function of the answering of the call by the desired subscriber, Iso that `after the release of relay U, ground would again be at the b-conductor which, however, would have no eiect on the relay X2 of the repeater Ue2.

In the repeater Ue2. (Fig. 3), 4upon termination of the last series of pulses, relay V2 releases. Relay V2 opens the circuit of relay Y2 at contact 29v2. During the release interval of relay Y2, relay H2 is energized in a circuit from -l, 30v2, 33312, 31x2, H2, Relay H2, over contact 10112 short circuits relay E2, winding 1I; relay E2 restores and transmits an A.C. pulse over contacts 13e2, 14e2 from the A.C. source WQ2 back to repeater Uel (Fig. 2). The A.C. pulse is terminated in the repeater Ue2 by the release of relay H2. After the release of relay H2, relay E2 actuates in series with the holdingre'lay'CZ. During therelease of relay E2, a circuit'is'closed'for relayfWZ from 26e2, W21, U21, After.' the actuationof relay E2, relay W2 is held energizedv in seriesiwithrelays C2 and E2 over a second winding, the short circuit of which is opened at contact 35w2, the circuit extending from C2, E211, 1c2, WZIII, Contact 17wt2 upon opening disconnects relay X2, rwinding 1,'iinally from Ithe b-conductor so that in case of any subsequent dialing by Ithe telephone oper ator, further testing operation of relay X2 on the bconductor is prevented. Further dialing by a subscriber will have no effect-as may be noted from the following explanations due to the dialing-conclusion si-gnal.

TheV pulse receivingrelay I1 in the repeater Uel, Fig. 2, energizes, in response to rthe dialing-conclusion pulse. Relay J|1` lby the closingA of it's contact jl energizes relay H1. Relay H1 short circuits relay M1 over contact 4111 and at the same time disconnects relay K1 at contact 3h1. 'I'he dialing-conclusion pulse, however, lasts only sutliciently long so that while relay M1 is caused to release, relay K1 continues to hold. As a result, relay G1 is energized over winding I in a circuit from 3v1, 3a1', 3m1', 4101, 2k1, GI, 4c1, Relay G1 remains energized over its winding 1, but the following holding circuit, independent of relay I-Il, is produced'over its Winding II from 2k1, 6g1, GlII, 4c1, During the ener-gization Iofl relay H1, ground is applied to the a-conductor over choke coil DrI and contact 7h1.

In the time-zone unit ZZ, Fig. 2, relay HZ, as a result, is energized in a circuit from DrI, 7h1, a-conductor, veel',` Hz, -Relay Hz connects relay TZ at contact hzl; relay TZ holds itself over its own contact tzl, and by opening'contact 1z3, opens the pulse repeater circuit to the repeater Ue1. At the same time by the opening of contact tz2, a further connecting of the control voltage to the b-conduct'or is prevented so that series of pulses which might now be transmitted by the calling subscriber can energize relays AZ and VZ, but further transmission thereof is prevented.

The further switching operations in connection with the establishment of connections are without importance for the presentinvention anddescription of such operation is therefore omitted.

The release of the connection is brought about by the calling subscriber restoring the receiver. The c-conductor to the time-zone device is thereupon interrupted in the first group selector, and relay Cz deenergizes. This results inzrelease of the seizure relay C1 in the repeater Uel.. In'the latter, the holding circuit of relay K1 is opened by opening contact 6c1. Relay K1 restores with a substantial time delay. During the release interval of relay K1, relay A1 is energized for a prolonged interval over its winding 111. Relay A1 transmits `a correspondingly prolonged A.C. pulse over the trunk line VL to the repeater Ue2. In repeater Ue2, relay I2 is energized for -a similar prolonged interval. Relay J2 energizes relay A2 for a like interval over contact 8j2. Relay C2 is accordingly short circuited for `such interval at contact 34a2 land releases. Relay C2 opens the c-conductor to the second group selector at contact 9tc42, relay -Cg in such group selector releasing. Relay Cg opens the cconductor to the connector LW2 at contact 3cg, causing release of relays C and G. By the release of relay C, test relay P is caused to restore in known manner, and thereupon the rotary magnet D is connected, which in cooperation with the second winding (not shown) of relay U returns the connector to normal.

Changes may be made within the scope and spirit of the appended claims.

What is claimed is:

1. In an automatic telephone system having a connecting device and serially successively related thereto a plurality of switching devices including a connector for selectively extending a call from va calling subscriber station, under control of impulse series transmitted from such calling station, to a desired 'called .subscribergsttion .which' is accessible. to said connector'tl1e respective Fswitching devices having line Yconductors:whiclrare re,- -sponsive to the Vextension of the'call tosaid connector switched through to extend to corresponding line conf ductors forming part of said connectorga circuit ar'- rangement for suppressing the effects of impulse series transmitted from the calling Vstation in excess of Vpulses -required for extending the'call to the desired'called station, said circuit arrangement comprisingmans Vin said connector for operatively connecting a predetermined potential to a line conductor thereof ,which potential is propagated, by way of such line conductor and rearwardly over corresponding line conductors of switching devices preceding said connector, to a predetermined' one of said switching devices, means in said connector jfor altering said potential at an instant prior to completion of the extension of the call to the vdesired called subscriber lstatlon, and switching means in said'predetermined one of `said preceding switching devices operatively responsive to the alteration of said potential for causing said connecting device to suppress impulse series transmitted from the calling station in excess of the impulse Yseries required for extending the call to the desired called station.

the last impulse series, and'means responsive to receipt of the last impulse series for opening another portion of said circuit means to keep said potential disconnected from said line conductor. i

4. A system and cooperation of parts according to claim l, comprising a circuit in said connector for normally maintaining a predetermined potential on a line conductor extending Vrearwardlyto said preceding switch- Ving devices, a control relay, means for actuating said control relay upon conclusion of receipt of the next to the last impulse series, means governed by said control relay for temporarily opening a portion of said circuit to disconnect said potential, and means responsive to receipt of the `last-impulse series for opening another/,portionof said circuit to keep said potential disconnected from said line conductor. *I Y Y l 5. A system and cooperation of partsY accordingrto claim 1, comprising a circuit in'said connector for Ynormally maintaining -a predetermined potential on a line conductor extending rearwardly to said'preceding switching devices, a control relay, means for actuating'said .control'relay upon conclusion of receipt of the next to the Vlast impulse series, means governed by said control relay for temporarily opening a portion of said circuit V.to disconnect saidrpotential, and means for thereafter opening another portion of said circuit Vto keep said poten- `tial disconnected from said line conductor. Y Y ,Y A

6. VA systemand cooperation of parts according to claim 1, comprising a relay in saidrpredetermined one of said preceding switching devices constituting Y said 'switching means, meansfor connecting said relay to a line conductorV incident to the transmission to s aid connector of the next to the last impulse series to test Vfor said predetermined potential, said relay energizing responsive vto said'potential. i y Y p' Y Y I' 7.7A system and cooperation of parts according' to claim 1, comprising a relay in said predetermined one of said preceding switching devices constituting saidV switching means, means for connecting said relay to a line con- Lductor incident to the transmission to said connector of the next to the last impulse series to test forl said predetermined potential, said relay energizing responsive vto said potential, and slow-to-release relay means for maintaining the energized condition of,Y said relay. 4 I

8.A system and cooperation of parts according `.to claim l, comprising a relay in said predetermined one 0f `said preceding switching devices constituting saidY switching means, means for connecting said relay toV a Aline conductor incident to the transmission to said connector vof the next to the last impulse series to test for the References Cited in the le of this patent UNITED STATES PATENTS Ostline May 19, 1953 2,655,559 Malthaner et al Oct. 13,1953 f 2,686,840 Den Hertog Aug; 17 1954 

